Holes will be punched.

February 12, 2009 6:41 AM

My RFID Metro Q fare pass (Houston, TX public transport) specifically instructs, "Please do not bend or punch holes in this card". I want to punch a hole in it anyway.

How can I figure out where exactly the chip is located so that I don't destroy it when I punch a hole in it? I suppose that it is an RFID mechanism because the card doesn't need to be swiped through a magnetic reader and doesn't have any visible stripes, it just gets tapped to a pad at the train station every time I ride. I am not sure how the cashier at my school reloads it.

It does have one tiny rectangle (approximately 5x4 mm) that is barely perceptibly raised from the surface. Can I assume that as long as I stay away from it, my card will retain its function?

It's the only way I won't lose it again; punching holes through my school ID & magnetic key to my lab and attaching them to a lanyard with my essential keys on it has been a lifesaver (yes, I am aware that I invalidated my driver's license, but I use it exclusively for identification anyway and I have a new, valid one in the car I occasionally drive--at least I don't have to get a new one every two months).

posted by halogen to technology (13 comments total)

The antenna may very well cover a majority of the surface. Take a look, for example, at this photo. The raised area you can feel is probably only the chip portion. The antenna needs to be relatively large in comparison.

Can you shine a very bright light through the card to get an idea about the layout?
posted by odinsdream at 6:51 AM on February 12

Not addressing your specific question, but maybe of help anyway: we recently got new ID cards at work, and were similarly instructed to not punch holes in the cards (the old card came with a hole in it). All employees were handed new lanyards with a rubber clamp at one end that caught onto the card without needing to punch a hole in it. I'm not turning up an example via Google, but did find this, which might work?
posted by AwkwardPause at 6:53 AM on February 12 [1 favorite has favorites]

"I am not sure how the cashier at my school reloads it." Reminds me of the MIT kids that hacked the Boston subway. But now onto the point: RFID cards typically come with two parts; The circuit and the antenna. The antenna is typically coiled along the inside of the card, usually taking up as much surface area as possible.

As long as you don't puncture the chip/circuit or the antenna, there's no reason why it would stop working.
posted by CapitalWasteland at 6:53 AM on February 12

I'm not a scientist but I think there is possibility more inside than just a chip. This video would seem to indicate that in at least some RFID cards there is an antenna. Of course in the same video, you can see that most of that stuff is contained on the periphery of the card, which may help your cause.

On preview: Beaten to the punch
posted by syntheticfaith at 6:53 AM on February 12

Alternatively, just get one of these sleeves and put the card in that, then punch holes in the sleeve.
posted by odinsdream at 6:53 AM on February 12

OK, this is pretty much what I was talking about. A clamp that hold the card without needing a hole.
posted by AwkwardPause at 6:58 AM on February 12 [1 favorite has favorites]

I have one of those cards! I carry it around in a bifold id holder thing attached to my keychain. I really wouldn't punch a hole in it.
posted by Neofelis at 7:05 AM on February 12

The antenna may very well cover a majority of the surface. Take a look, for example, at this photo. The raised area you can feel is probably only the chip portion. The antenna needs to be relatively large in comparison.

And in case you think "Hey, that photo makes the antenna look fairly small, take a look at this photo. In short, the antenna could be right near the card's edge.

At my workplace they issue plastic ID card holders to people who want to put their ID cards on lanyards
posted by Mike1024 at 7:24 AM on February 12

Most RFID cards have a loop antenna that runs near the circumference of the card, as seen here.

If you look carefully, you may be able to see where the loop is running and punch there. If you know the type of card (say prox HID or Mifare, as linked above), you will be able to find images of it on the internet and see where the wires run.
posted by fake at 7:26 AM on February 12

After it expires take it apart to find the location of the chip and antenna and then you will know how to punch a hole through next month's card.
posted by caddis at 8:28 AM on February 12

Houston Chronicle 11/17/06 sec B, pg. 1 names the vendor as ACS Transport Solutions, Inc.

ACS helpfully lists references and has a case study [PDF] on Houston's contactless terminal project. For confirmation, the picture at the bottom of page two has a photo of the Q Card. The case study says there's 500,000 Mifare 1 cards and 6 million Mifare UL cards.

The Chronicle article stated the city had ordered many more disposable cards than the Q cards so I think you have a Mifare 1 card. Here's an image of the antenna of that card. Note the tiny Texas logo on the card.

I strongly recommend you get a second card to test this on before doing it on your main card. Also be aware the hole can provide a snag point for anything inside any system that would need to pull the card into it. I gather that's not the idea with these though. It was a problem with mag cards.
posted by jwells at 8:56 AM on February 12

I was at Notre Dame a couple summers ago for a week; we ate in the school food service and were issued mag-stripe cards.

At the Notre Dame school bookstore, I bought a lanyard thing that was a holder for these lunch cards. It was a plastic widget with a slot in it that the mag card friction-fit into.

If this card of yours is the same thickness as a credit card, maybe your school bookstore has something similar.
posted by chazlarson at 2:24 PM on February 12

Or, cut a small tab from sturdy plastic [like maybe a margarine lid], Gorilla Glue it to the card, then punch your hole in that.
posted by chazlarson at 2:28 PM on February 12